SU941328A1 - Process for recovering lime from lime-stone slurry - Google Patents

Description

(S) METHOD FOR REGULATING LIME FROM KNOWN

Slime

The invention relates to a technique for the regeneration of lime from limestone sludge, mainly a filter cake of sugar production, and can be used in the food and chemical industries of the building materials industry, as well as other sectors of the national economy. There is a method for regenerating lime from the filter press of sugar mills, including pre-drying filter press, grinding it and subsequent calcination in the pulverized state 1. The disadvantage of the known method is that after grinding, the material has a polydisperse granulometric composition and is necessary before calcining the operation of separating the material into separate fractions, since much smaller warm-up time is required for small particles of a material than for large ones. This complicates the process and degrades the quality of the product. The closest to the invention is a method for regenerating lime from limestone sludge, mainly a filter cake of sugar production, including spray drying a part of the sludge with heat from the flue gas exhaust gases and utilizing exhaust gas after drying to clean the diffusion juice of the sugar production, mixing the dried sludge with the remaining part cuttings, roasting the mixture and cooling the obtained lime 2. A disadvantage of the known method is that the waste gases sent for utilization They contain a low percentage of carbon dioxide, of the genus (23.3-25), which excludes the possibility of using exhaust gases to purify diffusion juice in sugar production, since the minimum content of SOCs required for the implementation of the diffusion juice purification process in exhaust gases must be 30. The low carbon dioxide content in the exhaust gases is due to the fact that the drying of the sludge in the spray dryer and the drying of the mixture obtained in the mixer is due to the heat of the exhaust gases of the calcining unit. Therefore, it is necessary to burn the fuel necessary for drying all

the sludge mass from the initial humidity of 0-60% to the final zero humidity and for carrying out the CaCOa decarbonization process taking into account the thermal efficiency of the unit, which leads to an increase in the number of flue gas exhaust gases and, consequently, to a decrease in carbon dioxide content in the exhaust gases. In addition, the need to mix in a dry powder mixer, obtained by spray drying, with a slurry moisture content of 0-60 to form a mixture of moisture content of 16-17% complicates the process and increases the duration of the process. The known method also does not provide the possibility of obtaining finely granulated lime, since the mixing of the powder obtained by spray drying with sludge in the mixer leads to the destruction of the microgranules obtained by spray drying.

The purpose of the invention is to increase the carbon dioxide content to 3050% in exhaust gases and to reduce the duration of the process.

The goal is achieved by those. that according to the method of regeneration of limestone limestone sludge, mainly filtering sediment of sugar production, including spray drying part of the sludge with heat from the flue gas exhaust gases and utilization of exhaust gas after drying for cleaning the diffusion juice of sugar production, mixing the dried sludge with the remaining part of the sludge, roasting the mixture and cooling of the obtained lime, provides for spray drying the remaining part of the sludge in a separate unit with an autonomous heat supply. The regulation of carbon dioxide in the processed gases is carried out by varying the amount of sludge dried in a separate

It has the following chemical composition, wt.%: CaCl5 95, organic additives 5- To obtain 1 kg of lime (CaO). activity 90 consumes 1.83 kg of filter cake. (based on dry matter, taking into account 2% of dust removal). The sludge prepared from the filter cake is divided into two streams with a volume of 50 wt.% Each, and pumps 2 under pressure of 2025 atm are fed to the centrifugal nozzles 3. With the help of centrifugal mechanical nozzles, one stream of sludge is sprayed in a spray dryer t, and the other stream of sludge is in spray dryer 5- In the spray dryer 5, the sludge is dried with heat from the exhaust gases of the cyclone-vortex furnace 6 with a temperature of 720 ° C. Sludge is dried in a spray dryer by means of an autonomous heat carrier supply to burners 7 installed in the lower part of the dryer. Spray drying of two sludge streams is carried out simultaneously. Dried powdered material with a pellet size of 0.2-0.6 mm from the bottom of each spray unit with an autonomous heat supply t for drying. The drawing shows a flow chart of the process of lime regeneration from the filter cake of sugar production. Example. The filter cake from the vacuum filters of the sugar factory is fed to the mash 1, where it is diluted with water to obtain a slurry with moisture content kS%. Filtration sediment solid dryers 4 and 5 at points 8 are simultaneously fed into a vertical cyclone-vortex kiln 6. 8 cyclone-vortex kiln 6 the material is heated to 950-1000 with a stream of gases obtained from combustion - natural gas, in the burners 9 and decarbonated with formation of calcium oxide and carbon dioxide. The resulting lime at the bottom of the calciner enters the cooling in the fluidized bed cooler 10. The cooled finished product enters the finished product warehouse. The exhaust gases from the spray dryer 5, after being cleaned in the scrubber 11, are sent to purify the diffusion juice to obtain sugar into the saturator 12 and the exhaust gases of the dryer are directed to the atmosphere. Wherein

The COq concentration in exhaust gases sent to clean the diffusion layer is 33%. This is achieved by reducing the fuel consumption in the roasting unit to 0.09 kg of equivalent fuel per 1 kg of the finished product. This reduction in fuel consumption in the calcining unit becomes possible due to the fact that a part of 50 wt.% Of the sludge is dried due to autonomous heat supply in the spray dryer 4 Regulation of the absolute amount and percentage of carbon dioxide in the exhaust gases, within 30-50%, required for changing the type of raw material for obtaining sugar (sugar beet, sugar cane), is carried out by changing the amount of sludge dried in the spray dryer in the range of 20-80 wt.%.

The exclusion from the lime regeneration process of the operation of mixing dry loroshka with a slurry stream with moisture of kO-6Q%, the need for sequential drying of the slurry stream with 0-60% moisture and a mixture with a humidity of 16-17% significantly reduces the process time.

Experiments confirm the possibility of lime regeneration by. This method also increases the C0 content (j in the exhaust gases to 35-50%. The resulting lime is characterized by high reactivity (quenching rate not more than 5 min), high firing quality (the content of non-quenched grains is less than 1%). The granulometric composition is characterized by the absence of granules larger 1 mm and a particle size of less than 0.1 mm no more than 10%.

The use of the proposed method for the regeneration of lime from lime sludge provides, in comparison with known methods, an increased content of carbon dioxide in exhaust gases up to 30-50% and the possibility of using exhaust gases for cleaning diffusion

juice when receiving sugar; reducing the duration of the process of lime regeneration by eliminating the operation of mixing the dry powder

with a stream of sludge and the need for consistent drying of two streams of sludge with different humidity; the ability to adjust the content. carbon dioxide in waste

gases; production of finely granulated lime, since the granulated material obtained by spray drying is directly fed to the roaster.

Claims (2)

1. Method of lime regeneration from lime sludge, mainly filtering sediment of sugar production, including spray drying part of the sludge with heat from the flue gas exhaust gases and utilization of exhaust gas after drying to clean the diffusion juice of sugar production, mixing the dried sludge with the remaining sludge, roasting the mixture and cooling the resulting lime, characterized in that, in order to increase the carbon dioxide content to 3050% in the exhaust gases and reduce the process time, the rest of the sludge is spray dried in a separate unit with autonomous heat supply. 2. The method according to claim 1, characterized in that the regulation The carbon dioxide content in the exhaust gases is carried out by varying the amount of sludge dried in a separate unit with an autonomous heat supply for drying. Sources of information taken into account in the examination .one. USSR author's certificate number 82010, cl. From Ot To 1/02,. 2. US patent No. 3796791, cl. 23177 (С ОА В 1/02), published. .